Although most research investigating diversity courses focuses on attitudes toward racial minorities and women, these courses may also influence student attitudes toward lesbians and gay men. The current study assessed student awareness of heterosexual privilege, prejudice against lesbians and gay men, and support for same-sex marriage. Students (N = 143) in a general diversity course completed identical surveys during the first and last weeks of the semester. Participants in diversity courses exhibited increased heterosexual privilege awareness and support for same-sex marriage, as well as less prejudice against lesbians and gay men, during the last week of the semester compared to pretest levels. (Contains 2 tables.)